For the purposes of this application, a lithography system is understood as meaning an optical system or an optical arrangement that can be used in the field of lithography. Apart from a lithography apparatus, which serves for the production of semiconductor components, the optical system may be for example an inspection system for the inspection of a photomask (hereinafter also referred to as a reticle) used in a lithography apparatus, for the inspection of a semiconductor substrate to be structured (hereinafter also referred to as a wafer) or a metrology system, which is used for measuring a lithography apparatus or parts thereof, for example for measuring a projection system. The optical arrangement or the lithography system may be in particular an EUV lithography system, which is designed for used radiation at wavelengths in the EUV wavelength range of between about 5 nm and about 30 nm.
Reference is often made hereinafter two a movable (second) component or a moved/movable object in the form of a mirror, in particular an EUV mirror. In principle, however, the movable component may also be any other object or any other component or subassembly, for example optical elements such as lenses or prisms, wafer stages, parts of machine tools, further carrying frames or carrying structures for optical or non-optical components, etc.
The first component may be for example a carrying frame (known as a “force frame”) of the optical arrangement, which substantially absorbs all of the forces acting on the optical arrangement. The movable component is typically spring-mounted with respect to the carrying frame, or mechanically decoupled from it, so that ideally no forces or vibrations are transmitted from the carrying frame to the movable component. The first component may, however, also be some other component, for example a carrier component, which is spring-mounted with respect to the carrying frame of the optical arrangement or mechanically decoupled from it.
In the case of an EUV lithography apparatus, specifically in the case of an EUV lens for projecting an image of a mask onto a light-sensitive substrate, the sensitivity of the quality of the imaging with respect to the deformation of optical surfaces of EUV mirrors is particularly great. On the assumption that the optical design of such a lens is corrected to about 10 mλ, where λ denotes the operating wavelength, it follows that at an operating wavelength λ of about 13.5 nm there is a maximum allowed wave-front error of about 135 pm. This means that a deformation of the surface of an EUV mirror of about 50 pm already results in a significant wavefront aberration. Therefore, during the operation of an EUV lithography apparatus or an EUV lens, EUV mirrors are set in an suspended state, so that the forces and moments acting on the EUV mirror become as small as possible. This state of being suspended or being mechanically decoupled from the surroundings has the consequence that the EUV mirrors can in effect move freely between their end positions, which are typically defined by end stops, and may collide with the end stops. Particularly when transporting an EUV lithography apparatus, but also in the event of an earthquake, this can lead to damages to the EUV mirrors or other components.
In the case of conventional EUV lenses, this issue is solved by inverting them during transport. In this case, the forces that bring about a weight compensation and lead to a suspended state of the EUV mirrors in the operating position of the EUV lens or of the EUV lithography apparatus, and also the forces of the weight of the mirrors, add together to form an overall force or overall acceleration, which corresponds approximately to twice the acceleration due to gravity (2 g). In this way, the mirrors generally stay fixed in their vertical end positions up to an acceleration of the order of 2 g. In the case of greater accelerations, the EUV mirrors may however leave the end positions and again lie freely between the end positions, i.e. the fixing of the EUV mirrors is limited with respect to the tolerable shock loads. In the case of future EUV lenses, the EUV mirrors may possibly become so large and heavy that inversion of the EUV lens is no longer advisable or possible.
DE 10 2012 212 503 A1 discloses a lithography apparatus which has a first component and a second component and also a coupling device in order to couple the first component and the second component to one another. The lithography apparatus has a sensing device for sensing a movement of a base on which the lithography apparatus stands, and also a control device, which is designed to activate the coupling device in dependence on the sensed movement of the base in order to limit a movement of the second component in relation to the first component. For this purpose, the coupling device may have at least one adjustable end stop. The adjustable end stop may be brought into abutting contact with a second component in the form of a mirror in order to achieve a form-fitting fixing of the mirror with respect to a first component in the form of a carrying frame. It is intended by the fixing to avoid damage to the mirror in the event of a shock or in the event of shaking as a result of an earthquake.
DE 10 2014 215 159 A1 describes an optical arrangement with at least one optical element and with a carrier, on which the optical element is arranged movably in relation to the carrier. A fixing device, with which the optical element can be fixed in place with respect to the carrier, has at least one actuator of a shape memory alloy. The fixing device is designed as a transport lock, which fixes the optical element in place with respect to the carrier when the optical element is not being used.
DE 10 2011 087 389 A1 describes a positioning system with a stop for a component, for example for an optical element, the stop limiting the path of movement of the component and being adjustably designed. The stop can be adjusted in such a way that the distance of the component from a stop face of the stop is kept in a predefined range.